# contact (physical)

When two things are at the same place in space during time and their boundaries touch.

- Computed level: L4 (depth in the emergence graph, not abstraction)
- Status: review  ·  Domain: physics  ·  Arena: spatiotemporal

## Emergence
**Emerges from:** [space](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-space.extent), [time](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-time.dimension), [boundary](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-boundary.limit), [others](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-others.distinct-entities), [touch](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-touch.together)

**Through:** Two distinct entities with boundaries occupy the same region in space and time, causing their boundaries to touch, enabling mutual influence.

**Novel properties:**
- coincidence in space and time
- boundary adjacency
- potential for mutual change

## Examples
- The International Space Station's solar arrays physically contact debris at orbital speeds, causing micrometeorite pits visible on returned panels. *(engineering)*
- Two billiard balls touch momentarily after a break shot on a pool table at the 2023 World Nine-ball Championship. *(everyday life)*
- Neurons in a mouse hippocampus physically contact each other at synapses, verified via electron microscopy in a 2017 Max Planck study. *(biology)*

## Used by
- [carrying](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-carrying.transporting) (L5)
- [charged](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-charged.electrical) (L5)
- [held](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-held.grip) (L5)
- [join](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-join.connection) (L5)
- [press](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-press.force) (L5)

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*Canonical: https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-contact.physical*  
*Structured data: https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-contact.physical.json*  
*Every definition provably resolves to space, time, energy and pattern.*